Defibrillators appear to work in medical helicopters

NEW YORK (Reuters Health) - Despite concerns about using heart defibrillators in a moving ambulance, a new study suggests the potentially life-saving devices may work just fine in "medevac" helicopters.

The study, published in the journal Resuscitation, showed automated external defibrillators (AEDs) were consistently correct in reading simulated heart-rhythm disturbances in a flying helicopter.

AEDs are portable devices that automatically analyze the heart's rhythm and, if needed, instruct the user to deliver a shock. That shock can be life-saving to a person in cardiac arrest, which is usually caused by a heart-rhythm disturbance called ventricular fibrillation -- where the heart begins to quiver chaotically and can no longer pump blood to the body.

A recent study using pigs and computerized mannequins as test subjects found that AEDs might not work reliably in a moving ambulance. Bumps in the road could create vibrations that the AED might misinterpret as a heart arrhythmia.

But in the new study, Korean researchers found no problems with AEDs used in an in-flight medevac helicopter.

In one part of the study, the researchers used a mannequin and a device that simulates heart-rhythm disturbances to test three AEDs made by different manufacturers. They found that all three devices correctly recommended a shock when needed.

The researchers also tested the AEDs on a volunteer who simulated a motionless patient in transport. All of the devices correctly read the volunteer's heart rhythm as normal and didn't recommend a shock be delivered.

The better performance of AEDs in moving helicopters versus ambulances may come down to the fact that there are no road bumps in the air.

Compared with the earlier ambulance study, the mannequins in the current one had less vibration in the chest while the helicopter was in motion, explained researcher Dr. Incheol Park of Yonsei University in Seoul.

These latest findings are "encouraging," according to Park's team, but further studies are still needed to confirm the safety of using AEDs in moving helicopters.

If possible, Park told Reuters Health by email, it would be helpful to measure AED performance under harsher conditions -- like higher altitudes and bad weather.

As it stands, there are no specific guidelines on AED use in medevac helicopters, Park said.

But since helicopters are typically used to transport critically ill patients, the chances of having to treat cardiac arrest onboard are relatively high.

Past studies have suggested that between 3 percent and 5 percent of patients being moved by air suffer cardiac arrest at some point during transport, with up to 18 percent undergoing defibrillation.